Under present roofing practices in which a pitch pocket is used to seal a pipe to a roof opening, leaks are quite common and there is a very high percentage of leaks within the first six months after installation. Sealants crack or run off because of ever-changing weather conditions. Pipe and roofing materials expand and contract with temperature changes and there are also relative movements such as vibrations from wind and/or machinery. If oftentimes happens that leaks are not discovered until after substantial damage has occurred, making major repairs necessary.
Roof curb devices have been provided for obtaining a proper seal but have generally be designed for new construction or during installation of a new roof and they are difficult to install and not at all suitable for extending a pipe through an existing roof.